title: Real-time CARS imaging reveals a calpain-dependent pathway for paranodal myelin retraction during high-frequency stimulation.
abstract: High-frequency electrical stimulation is becoming a promising therapy for neurological disorders, however the response of the central nervous system to stimulation remains poorly understood. The current work investigates the response of myelin to electrical stimulation by laser-scanning coherent anti-Stokes Raman scattering (CARS) imaging of myelin in live spinal tissues in real time. Paranodal myelin retraction at the nodes of Ranvier was observed during 200 Hz electrical stimulation. Retraction was seen to begin minutes after the onset of stimulation and continue for up to 10 min after stimulation was ceased, but was found to reverse after a 2 h recovery period. The myelin retraction resulted in exposure of Kv 1.2 potassium channels visualized by immunofluorescence. Accordingly, treating the stimulated tissue with a potassium channel blocker, 4-aminopyridine, led to the appearance of a shoulder peak in the compound action potential curve. Label-free CARS imaging of myelin coupled with multiphoton fluorescence imaging of immuno-labeled proteins at the nodes of Ranvier revealed that high-frequency stimulation induced paranodal myelin retraction via pathologic calcium influx into axons, calpain activation, and cytoskeleton degradation through spectrin break-down.
authors.affiliation: Department of Chemistry, Purdue University, West Lafayette, Indiana, United States of America.
authors.forename: Terry B
authors.initials: TB
authors.lastname: Huff
authors.forename: Yunzhou
authors.initials: Y
authors.lastname: Shi
authors.forename: Wenjing
authors.initials: W
authors.lastname: Sun
authors.forename: Wei
authors.initials: W
authors.lastname: Wu
authors.forename: Riyi
authors.initials: R
authors.lastname: Shi
authors.forename: Ji-Xin
authors.initials: JX
authors.lastname: Cheng
mesh_terms: D015761:4-Aminopyridine / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001369:Axons / Q000187:drug effects / Q000201:enzymology; D002118:Calcium / Q000378:metabolism; D002154:Calpain / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000378:metabolism; D004558:Electric Stimulation; D004789:Enzyme Activation / Q000187:drug effects; D006168:Guinea Pigs; D066298:In Vitro Techniques; D009186:Myelin Sheath / Q000187:drug effects / Q000201:enzymology*; D015398:Signal Transduction / Q000187:drug effects; D013059:Spectrum Analysis, Raman / Q000379:methods*
chemical_list: D003598:Cytoskeletal Proteins; D015761:4-Aminopyridine; D002154:Calpain; D002118:Calcium